Boron fuel-salt smoke-producing compositions



3,475,237 BORON FUEL-SALT SMOKE-PRODUCING COMPOSITIONS George A. Laneand William A. Smith, Midland, and

Ralph B. Van Wert, Essexville, Mich., assignors to The Dow ChemicalCompany, Midland, Mich., a corporation of Delaware No Drawing. FiledJuly 1, 1968, Ser. No. 741,244

Int. Cl. C06d 3/00; C06b 11/00 US. Cl. 149-22 4 Claims ABSTRACT OF THEDISCLOSURE The present disclosure relates to smoke-producing pyrotechnicpressed grain compositions consisting of a boron-containing fuel-and anorganic or inorganic oxidizer.

BACKGROUND OF INVENTION In wartime the armed forces frequently find itnecessary to employ smoke screens to shield troop movements from theenemy.

Presently, the active ingredients in smoke-screening devices are whitephosphorus, titanium tetrachloride, chlorosulphonic acid, sulfurtrioxide, zinc chloride, and oils. All of these agents, with theexception of the oils, react with the atmosphere to produce smokes whichare both corrosive and toxic. Oil smokes, while non-toxic andnon-corrosive demonstrate relatively poor obscuring power.

An object of the present invention is to produce pyrotechniccompositions which can be ignited to yield voluminous and densescreening smokes which are noncorrosive and relative non-toxic.

SUMMARY OF THE INVENTION The pyrotechnic smoke producing composition ofthe present invention consists by weight of from about 25 percent toabout 75 percent of a boron-containing fuel compound with the balancebeing an organic or inorganic oxidizer.

The boron-containing fuel is generally a member selected from the classconsisting of elemental boron, boron carbide, boranes containing fromabout 5 to about boron atoms per molecule, and mixtures thereof.Additionally, boron silicides and other compounds consisting essentiallyof boron and silicon can be employed as fuels in the present invention.

Methyl borate and trimethoxyboroxine can also be employed in the presentinvention as boron-containing fuel compounds. Because of the liquidnature of methyl borate and trimethoxyboroxine, it is desirable todisperse these compounds within particulate inert absorbent carriercompounds such as expanded clays, alumina, and porous silicates. Saidparticulate carrier compounds containing the boron fuel can be admixedwith the particulate oxidizer homogeneous, and the so-homogenized blendcan be placed in a suitable container and compacted under pressure. Theresulting pressed grain munition can be initiated with a commonlyemployed ignition system.

Generally the oxidizer employed is a member selected from the groupconsisting of the alkali metalor ammonium nitrates, -chlorates and-perchlorates, guanidine nitrate, and mixtures thereof. Preferably,where an inorganic oxidizer is employed, said oxidizer will besubstantially anhydrous, although hydrated inorganic oxidizers areoperable in the present invention.

Both oxidizer and fuel should be in a particulate form and whileparticles of almost any size can be employed in the present invention,smoke production efliciency in- Patented Oct. 28, 1969 creases asparticle size decreases. Generally, the particle size of the materialsranges from about 5 to about 400 microns.

The pyrotechnic smoke-producing compounds of the present invention canbe fabricated by admixing the particulate boron-containing fuel andparticulate oxidizer until a substantially homogeneous blend isobtained. The so-homogenized blend is enclosed in a suitable containerand compacted by conventional means to about 2000 p.s.i. The resultingcompressed grain is initiated with commonly employed ignition systemsuch as a fuse.

PREFERRED EMBODIMENTS A preferred embodiment of the present inventioncomprises a pyrotechnic smoke producing munition comprising on a weightbasis of from about 30 to about 70 percent of elemental boron, and fromabout 70 to about 30 percent of a member selected from the groupconsisting of alkali metaland ammonium nitrates, -chlorates,-perchlorates and mixtures thereof.

Very good smoke production can be obtained where about 40 percent byweight of the munition is substantially anhydrous lithium perchlorate or.sodium perchlorate and the balance is boron.

Another preferred embodiment of the present invention is thesmoke-producing munition consisting by weight of from about 25 to about70 percent boron carbide, and from about to about 30 percent of aninorganic oxidizer selected from the group consisting of alkali metaland ammonium nitrates, chlorates and perchlorates. Most preferably, theoxidizer will be substantially anhydrous lithium perchlorate.

Still another preferred embodiment is the pyrotechnic compositionconsisting by weight of from about 25 to about 65 percent of particulatedecaborane fuel and from about 75 to about 35 percent of a memberselected from the group consisting of guanidine nitrate, anhydrouslithium perchlorate, and mixtures thereof, as oxidizer.

To fabricate the pyrotechnic munitions described directly hereinabove,the particles of oxidizer and fuel are admixed until substantiallyhomogeneous, placed in a heat resistant container and compacted bycommonly employed means to about 2000 p.s.i. and the resulting pressedgrain is initiated with a commonly employed ignition fuse.

The following examples are set forth to illustrate the present inventionand are not intended as limits thereto.

Example 1 Upon ignition, the burning time, aerosol yield Agent inAerosol Form Aerosol yleld (percent)- Total Weight Composition andefiiciency,

Agent in Aerosol Form 100 Agent in Composition were measured.Additionally, the total obscuring power (TOP) of each munition wasmeasured in terms of area obscured per pound of munition employed.

Upon ignition, the efiiciency of dissemination was about Efficiency(percent) 55 percent, the yield was about 100 percent, and the obscuringpower was about 5500 ft. obscured per pound of munition employed.

It should be noted that smoke production and obscuring power increase asthe relative humidity increases. The above experiment was carried out ata relative humidity of about 55 percent.

4, Example 5 Employing a process of fabrication substantially similar tothe process set forth in Example 1, various samples were prepared andtested to compare obscuring power with the obscuring power produced by astandard titanium chloride composition. The test results are set forthin Table V.

TABLE V Munition Composition (parts by Efiiciency, Yield, TOP} Burningweight) percent 1 percent 2 {ti/lb. Time, sec.

Run N 0.:

1 60 Boron/50 LiClO4 55. -100 6, 000 1 2 65 B1oH14/35 guanidine 60 -l004, 800 3 T1Cl4(c0ntrol) 4, 100

' 1 Efficiency, percent conversion of fuel to smoke.

2 Yield, percent of smoke generted from a given weight of munition. TOP,total obscuring power, itJ/lb.

Example 2 Employing a process substantially similar to the processdescribed in Example 1, other samples were prepared wherein the relativeamounts of boron fuel and lithium perchlorate oxidizer were varied. Uponignition these samples yielded the data set forth in Table I.

TABLE I Composition Results Total obscuring Boron, wt. LiClO4,wt. Powerpercent percent (TOP) ftfl/lb From Table I it can be seen that for thisfuel and oxidizer optimum obscuring power is obtained when thecomposition consists by weight of about 60 percent elemental boron andabout 40 percent lithium perchlorate. The particle size of fuel andoxidizer employed ranged from about 5 to about 200 microns.

Example 3 Employing substantially the process set forth in Example 1, amunition grain consisting of about 55 grams of elemental boron and about45 grams of NaClO was prepared and ignited. The total obscuring powerwas about 5,900 ft. /lb. of munition employed. The relative humidity atthe time of ignition was about 65 percent.

Example 4 TABLE II Composition B 0, wt. LiClO wt. Percent PercentResults obscuring Power, ti/lb.

From Table II it can be seen that optimum obscuring power is obtainedwhen this munition consists by weight of about 30 percent boron carbideand about 70 percent lithium perchlorate.

From Table V it can be seen that compositions of the present inventionproduce obscuring smoke screens substantially equivalent to thoseproduced by titanium chloride.

The examples set forth directly hereinabove are intended solely asillustrations and not as limitations upon the present invention, forsaid invention is limited only by the appended claims.

We claim:

1. A pyrotechnic smoke-producing composition consisting essentially byweight of from about 25 to about 75 percent of a fuel selected from thegroupconsisting of elemental boron, borane compounds containing fromabout 5 to about,10 carbon atoms per molecule, methyl borate,trimethoxyboroxine, and mixtures thereof, and from about 30 to 70percent of a particulate oxidizer selected from the group consisting ofalkali metaland ammonium-perchlorates, -chlorates, and -nitrates',guanidine nitrate, and mixtures thereof, as oxidizer.

2. A pyrotechnic smoke-producing composition consisting essentially ofby weight from about 30 to about 70 percent particulate elemental boronas fuel, and from about 70 to about 30 percent of an oxidizer selectedfrom the group consisting of alkali metalor ammonium perchlorates,-chlorates, -nitrates and mixtures thereof.

3. The composition as defined in claim 2 wherein about 40 percent byweight is an oxidizer member selected from the group consisting ofsubstantially anhydrous lithium perchlorate and sodium perchlorate, andthe balance is boron.

4. The composition defined in claim 1 wherein from about 25 to about 65percent of decaborane as fuel compound, and from about to about 35percent of an oxidizer member selected from the group consisting ofguanidine nitrate and anhydrous lithium perchlorate.

References Cited UNITED STATES PATENTS Martinez et al 149-22 X CARL D.QUARFORTH, Primary Examiner S. J. LECHERT, Assistant Examiner US. Cl.X.R.

